<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="style.css">
    <style>
        .header{
            height:35px;
            background: #f5f5f5;
            line-height: 35px;
            font-size: 16px;
            text-align: center;
        }
        .main{
            width:1000px;
            margin: 0 auto;
        }
    </style>
</head>
<body>
   <div class="header">
       <div class="main">这是头部</div>
   </div> 
</body>
</html>